Does what it states. . . puts a waterproof layer on your canvas boat top. Use rubber or latex gloves since you should not get this stuff on your skin and don't spray it on when there is any wind so you breath in as little as possible. Spayed it on my boat top and let it dry the stated hours and put it back on the boat. It rained two days later and my white boat has black streaks all over it from the top. . . but it did keep the inside of the boat dry.